I listened to Cardi speak and will say that she isn't the most articulate woman in the music game, but I do agree with her regarding preferences. A person can like what they like, but it should not be at the expense of putting down those outside their preference.
As far as her using the n-word..
I am not sure if I would trip. I would tell her that some Black people may take exception to her using that word around them, so make sure she has some sort of rapport with people before using that word.
I uunderstand that some regions, cities, neighborhoods, etc. has different politics and the usage of the n-word as well as who can use it varies. From my understanding, it is more common for Latinos to use that word w/o any pushback from Black folks in certain areas than places where there is little to no Latinos.
It is a complex dynamic, so if a non-Black is gonna use it, then do so knowing that there may be funk/smoke that may come about from using it.